linux-kernel - [PATCH rcu 18/20] srcu: Document that srcu_{read_lock,down_read}() can share srcu

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Message-Id: <20250224022214.12037-19-boqun.feng@gmail.com>
Date: Sun, 23 Feb 2025 18:22:12 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: rcu@...r.kernel.org
Cc: Lai Jiangshan <jiangshanlai@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	bpf@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>
Subject: [PATCH rcu 18/20] srcu: Document that srcu_{read_lock,down_read}() can share srcu_struct

From: "Paul E. McKenney" <paulmck@...nel.org>

This commit adds a sentence to the srcu_down_read() function's kernel-doc
header noting that it is permissible to use srcu_down_read() and
srcu_read_lock() on the same srcu_struct, even concurrently.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: <bpf@...r.kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 include/linux/srcu.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index a0df80baaccf..317eab82a5f0 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -359,7 +359,8 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
  * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.
  *
  * Calls to srcu_down_read() may be nested, similar to the manner in
- * which calls to down_read() may be nested.
+ * which calls to down_read() may be nested.  The same srcu_struct may be
+ * used concurrently by srcu_down_read() and srcu_read_lock().
  */
 static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
 {
-- 
2.39.5 (Apple Git-154)